Automakers and suppliers say a U.S. push to broaden Wi-Fi use could jam accident prevention technology that may cost as little as $100 per vehicle and save thousands of lives annually.

The Federal Communications Commission next week may propose rules to let new users into airwaves near those allocated since 1999 to developing car-to-car wireless communications. That technology, now being road-tested in Ann Arbor, may be the precursor to self-driving vehicles.

Trade associations representing automakers including Ford Motor Co. and Toyota Motor Corp., along with suppliers including Delphi Automotive Plc, Denso Corp. and Robert Bosch GmbH, signed a letter being sent today to FCC Chairman Julius Genachowski protesting his plans for the new Wi-Fi spectrum.

Supporters of talking-cars technology, who have spent more than a decade and hundreds of millions of dollars developing it, say opening nearby airwaves to other users may cause interference in an area with no margin for error.

The technology lets cars talk with each other at short range to know when two are approaching an intersection, are about to collide in adjacent lanes or are approaching a vehicle up ahead too quickly. Automakers say the systems could be installed in new cars at a cost of about $100 a vehicle or sold as after-market devices.

“We’ve really worked hard,” Scott Belcher, CEO of the Intelligent Transportation Society of America, a Washington, D.C.-based group that advocates for transportation safety, said in an interview. “We’re finally at the point where we’re going to see benefits. And we may put it all at risk without knowing the answer. What we fear is a decision gets made without the necessary due diligence.”

On Jan. 9, Genachowski said the agency wants to allow Wi-Fi services in a section of airwaves that already includes similar uses, as well as the experimental auto industry frequencies. The plan for Wi-Fi, an aerial Internet connection found globally in coffee shops and offices, is part of President Barack Obama’s strategy to expand airwave-sharing to cope with a shortage of frequencies.

“As this spectrum comes on line, we expect it to relieve congested Wi-Fi networks at major hubs like convention centers and airports,” Genachowski said in remarks distributed by email. The FCC is to vote Feb. 20 on his proposal to form rules, according to the meeting’s agenda.

FCC supporters say airwaves users must adapt and share by using technologies that can gather intended signals and disregard stray transmissions.

Connected-vehicle technology is being tested in Ann Arbor on almost 3,000 cars, trucks and buses. The U.S. Transportation Department has spent millions of research dollars developing the technology in partnership with the private sector, and auto safety regulators may decide by the end of this year whether to require it in new vehicles.

“There’s a great potential here to reduce not only fatalities and injuries but also less severe crashes that can cause a lot of congestion on the highways, too,” said Michael Cammisa, safety director for the Association of Global Automakers, whose members include Toyota and Honda Motor Co., both members of a government-industry group developing the technology.

“Those potential benefits might not be realized,” Cammisa said. “We’re concerned about potential for interference if these other devices are also using the same spectrum.”

The National Highway Traffic Safety Administration, the U.S. agency that regulates auto safety, has said 80 percent of crashes involving drivers who aren’t impaired could be prevented or reduced in severity if vehicles were equipped with these systems.

“We support efforts to identify spectrum that may be utilized to expand Wi-Fi applications,” the auto industry trade groups said in Wednesday’s letter to Genachowski. “But with over 30,000 deaths on our nation’s roads every year, we also believe it is critical that efforts to open up additional spectrum do not come at the expense of revolutionary life-saving technologies.”

The Transportation Department “is aware of the FCC’s proposed action to open up” the spectrum, Karen Aldana, a spokeswoman for NHTSA, part of the Transportation Department, wrote in an email.